1. Field of the Invention
This invention relates to a thermostatically-regulated power control arrangement for, and method of, switching an electrical power source to a heating/cooling system load. More particularly, this invention relates to a method of installing the power control arrangement at an electrical outlet box, as well as to a retrofitting method of replacing a line voltage thermostat with a low voltage thermostat.
2. Description of the Prior Art
A conventional heating/cooling system load, such as a hot water circulator, is typically controlled in many homes by a line voltage thermostat operative for sensing the temperature in a room whose temperature is to be regulated, and for cycling the circulator on when the room temperature falls below a preset temperature, and for cycling the circulator off when the room temperature rises above the preset temperature. The preset temperature is manually set in advance to a single temperature value. The conventional line voltage thermostat is a simple on-off heavy-duty switch connected in series between the circulator and an electrical power source, and operative to conduct the maximum current required by the circulator. The conventional line voltage thermostat is mounted on a wall of the room in front of a convenient electrical outlet box to which a load wire from the circulator and a hot wire from the power source are routed for connection to the thermostat switch.
Although generally satisfactory for its intended purpose, the conventional line voltage thermostat has not proven to be an altogether practical fuel-efficient device for the reason that once the thermostat has been manually set to the preset temperature, it must be manually reset if the resident wishes to change the temperature. To improve fuel efficiency, a resident may wish to change the preset temperature several times during every day/night cycle. For example, the resident may wish to lower the preset temperature at night to sleep cool, or to have the preset temperature raised in the morning to wake up to comfort. Alternatively, the resident may wish to lower the preset temperature during the day while away from home, or to have the preset temperature raised at dusk just before returning home. In these and countless other situations, energy is wasted if the resident forgets to, or simply chooses not to, or is unable to, timely reset the thermostat. In any event, the manual adjustment of the preset temperature on conventional line voltage thermostats is, at best, a coarse one, thereby further contributing to the overall inefficient operation.
To improve fuel efficiency, clock-controlled, programmable, setback-type thermostats have been proposed for automatically maintaining one of two preset temperatures as a function of time. The clock-controlled thermostats are separately adjustable and programmable such that the resident may select a low preset temperature for any one desired time period, and may select a different high preset temperature for any other desired time period. Typically, during the winter heating season, the clock-controlled thermostat is set and programmed to automatically lower the temperature at night, and to raise it in the morning. Inasmuch as the clock-controlled thermostat typically has a thermostat switch designed to switch low voltage and low current, switching relays have always been used with this type of thermostat. The switching relay includes a transformer for lowering the incoming high line voltage to the low voltage which can be safely switched by the thermostat switch, and a relay having a heavy-duty relay switch which can safely handle the high voltage and current required by the heating/cooling system load.
Although generally satisfactory for their intended purpose, the clock-controlled thermostats and associated switching relays have not proven to be altogether practical in terms of home installation. The known switching relays must be installed in the home by being connected to three different wires, namely, the hot, neutral and load wires. The hot and neutral wires are connected to a power source, typically at the circuit breaker box in the basement of a house. The load wire is connected to a hot water circulator, typically located in the basement near the furnace and boiler of the heating/cooling system. Hence, for practical reasons, the known switching relays are always installed in the basement where the aforementioned hot, load and neutral wires are all present.
There are many difficulties associated with the requirement of installing the switching relay in the basement. First of all, it is often difficult for a homeowner or electrician to even find the hot, load and neutral wires in the basement, particularly when the latter is crowded and unlit. Secondly, the wiring is often concealed in a finished basement, and is typically not available at exposed locations, thereby requiring the breaking of walls to expose the wiring. This is not only an expensive undertaking, but is also highly undesirable, particularly when the basement is finished. Thirdly, the homeowner himself, or an electrician's helper, may not be qualified or skilled enough to properly connect the three wires to the switching relay. Fourthly, some homeowners object, for reasons of safety, to the mere fact that an electrician must enter the basement to make the necessary three-wire connection between the switching relay and the circulator. Fifthly, the cost of basement installation is typically very expensive and time consuming not only due to the aforementioned wiring difficulties, but also due to the fact that the prior art switching relay is itself a large, expensive component. Finally, in the event that a homeowner wishes to replace the conventional line voltage thermostat with the more modern clock-controlled thermostat, the aforementioned wiring difficulties, safety aspects and high expense of installation may cause the homeowner to forego the retrofitting installation, thereby wasting fuel and energy.